The research proposed for this award will examine how spatial attention modulates cortical circuit activity in the early visual system. The proposed studies link the candidate's scientific background and future career objectives by examining intentional modulation of neuronal activity at multiple processing levels. Intentional effects will be observed at the individual cellular level (Aim 1), the local circuit level (Aim 2), and the cortical population level (Aims 1 and 3). By employing this novel approach toward understanding attention within the context of cellular and circuit processing, the candidate will draw upon experience across all phases of her research career. During the mentored phase of the proposed award, the candidate will simultaneously examine 1) how spatial attention modulates synaptic efficacy in cortical neurons receiving afferent thalamic input, and 2) how changes in cortical ensemble activity relate to the arrival of afferent information in attentive and non-attentive states. Through the instruction of two co-sponsors, one an expert in spatial attention task design/implementation/analysis and the other an expert in multi-electrode recording techniques/analysis, and with the vast resources already available at the University of California, Davis, the training received during the mentored phase will be invaluable to the longer-term objectives outlined in the independent phase of the proposal. As an independent investigator, the candidate will continue to address questions of functional dynamics in early visual cortical circuits using spatial attention tasks and multi-electrode recording. These experiments will further explore 1) whether and how the effects of spatial attention differ across neuronal cell types and local circuit levels, and 2) whether and how ongoing cortical network activity influences these intentional effects. All experiments proposed will be undertaken in the early visual system of awake-behaving monkeys, an ideal model for a number of reasons. First, while spatial attention influences early visual system activity, little is known about the mechanisms involved. Second, there is a wealth of knowledge available about the primate visual system. Third, the awake-behaving animal paradigm allows for the assessment of functionality in the fully cognizant state. Fourth, and most importantly, the primate visual system is similar to that of humans and therefore provides an ideal model for human cognition.